PIN AND SOCKET ELECTRICAL CONNECTOR

Abstract: A socket (10) has a collet (46) housed in a bore (48) for receiving an end (58) of a pin (8). The collet (46) has legs (60) projecting into the bore, in a direction away from the bore opening (48), to grip the pin end (58) when it is inserted in the bore (48). The collet bears on a shoulder (58) in the bore and is held in place by rounding the end (56) of the socket. The arrangement requires a relatively low insertion and extraction force. The socket (10) need not be of springy material and precious metal coatings may be applied more sparingly to the contacting parts.

Description: PIN AND SOCKET ELECTRICAL CONNECTOR The present invention relates to a pin and socket electrical connector. The widely used prior art form of pin and socket contact in electrical connectors comprises a socket formed by a cylindrical body which is slit along its length from one end to form two leaves which are then closed together. The pin has a rounded nose which urges the two leaves apart as it is inserted into the socket, the leaves gripping the pin to make the electrical contact. A sleeve is fitted around the split end of the cylindrical body to limit the outward movement of the leaves. Connectors using contacts of this design have a relatively high insertion and extraction force. This can lead to difficulties when mating connectors whi-ch utilise several pin and socket contacts. For example, when a large force is required to mate the two halves of a connector, the existence of mis-mating may not be apparent, and the connector may generally be subject to rougher handling, particularly in harsh environments. The socket must be made of spring material, such as a springy brass material. This causes difficulty when the design calls for a wire to be crimped to the free end of the socket. Also, a relatively thick silver coating is required along a substantial part of the socket, to ensure good electrical contact, which increases the cost of the pin and socket contact, and hence the connector. GB-A-614012 describes a plug and socket contact using a corrugated insert in the socket which is arranged to hold the pin within the socket. GB-A-659447 shows a plug and socket in which the socket is flanged to hold an apertured disc having prongs which grip the socket. US-A-4973272 describes a socket having a waisted collet which grips the pin. The system is designed to have a high insertion and extraction force. EP-A-476848 shows one pin and socket contact using a collet with tines which extend away from the collet body, into the socket bore. In another embodiment, the tines are pressed from the collet body and extend into the bore in the direction of thge socket opening. The end of the collet is waisted to protect the ends of the tines as the pin is inserted. These designs suffer various drawbacks, such as requiring high insertion forces and complex collet shapes. The present invention provides a pin and socket electrical connector comprising a pin, a socket comprising a body having a bore for receiving the pin and a collet housed within the bore and arranged to grip the pin when it is received in the bore, to form an electrical contact between the pin and socket body. By providing the collet in the bore, it is no longer necessary for the socket and body to be made of springy material, and the amount of gold or silver coating required on the parts can be reduced. The collet can be formed of a relatively thin gauge material (for example, 0.096-0.13mm, 0.0038-0.0052 inch) and a significantly lower insertion and extraction force is required compared to the prior art design. Preferably the collet is in the form of a split collar and has one or more legs which extend radially into the bore to bear on the inserted pin. The collet is of springy material arranged to be compressed as it is positioned in the bore, so that it springs out to fit snugly against the wall of the bore. Preferably the collet rests on a ledge in the bore, and the open end of the bore is closed slightly by rounding over to retain the collet in the bore. The rounding over will guide the pin through the collet and into the bore, protecting the collet against damage if the pin is being inserted at an angle. The arrangment of this invention provides a particularly simple and cost effect pin and socket contact design. Preferably the collet has two substantially diametrically opposed tangs. Preferably the tangs subtend an angle of from 30 to 60 degrees at the socket axis and more preferably about 45 degrees. Preferably the end of a tang projects into the bore by about 10 to 30 percent of the bore diameter, and more preferably about 15 to 25 percent and particularly about 20% percent of the bore diameter. Preferably the collet has a gold coating of thickness about 0.5 to 1.0 μm, and preferably 0.75 to 0.875 μm. Preferably the pin and socket are each coated in the region of contact with the collet, (when the electrical contact is made), with a coating of thickness about 0.1 to 0.3 μm of gold, and preferably about 0.2μm. The invention will be further described by way of example with reference to the accompanying drawings, in which : Figure 1 shows in part cross-section a multi-contact, bayonet locking, pin and socket electrical connector forming a preferred embodiment of the invention; Figure 2 shows a pin and socket contact of the embodiment of Figure 1, partly cut away and Figure 3 shows a collet of the contact of Figure 2. Referring to Figure 1 of the drawings, a pin and socket electrical connector 2 is in two halves 4, 6. The connector halves 4, 6 carry respectively a plurality of pin contacts 8 and cooperating socket contacts 10 (only one of each is shown in Figure 1) which will be described in more detail with reference to Figures 2 and 3. The connector half 4 comprises a cylindrical aluminium alloy body shell 12 which carries a dielectric insulator insert 14 of polychloroprene (a non-halogenated dielectric insert may be preferred for some applications, e. g. where there is a significant risk of a surrounding fire). The insert 14 is form locked in position in the shell 12 and a plurality of the pin contacts 8 is mounted in the insert 14. Wires 16 are attached to respective pin contacts 8 and may be sealed and gripped by a sleeving accessory 18, which has a heat shrink fitting. The pin contacts 8 have a reduced diameter central body portion 20 which is a tight fit in a bore in the dielectric insert 14, and larger diameter portions 21 at each end of the portion 20, to hold the pin contacts 8 in position against axial movement. A collar 22 of a bayonet coupling is mounted on the sleeve 12, to rotate freely around the sleeve 12, the collar having an inner rim 24 which will bear on a flange 26 on the sleeve 12. The collar 22 carries three roller spindles 28. The other half 6 of the connector 2 comprises an aluminium alloy sleeve 30 which carries a polychloroprene dielectric insert 32. A plurality of socket contacts 10 is mounted in the insert 32, corresponding to the pin contacts 8. Wires 34 are attached to the ends of the socket contacts 10. The sleeve 30 has arcuate tracks 36 in which the rollers 28 of the collar 22 are engaged. The collar 22 is rotated to draw the connector halves 4, 6 together. Stainless steel pins 38 are provided at the innert ends 40 of the racks 36. These provide an audible indication as the rollers 28 ride over the pins 38. A visual indication, such as red dots 42 may be used also to show that full locking has occurred. The construction thus far described is well known in the art, and exemplified for example in the ABB M. S. bayonet connector series marketed by AB Connectors Limited of the U. K. It will be appreciated that a screw nut coupling may be used in place of the bayonet coupling described. Referring to Figures 2 and 3 of the drawings, a pin and socket contact 8, 10 forming a particular feature of the invention will be described. The socket 10 has a body 44 and a collet 46 inserted in a bore 48 in the body 44. The bore 48 is of circular cross-section and is formed at one end of the body 44 and is sized at its inner end 50 to receive snugly a pin end 52 of the pin 8. The bore 48 has an enlarged cylindrical region 54 near its open end 56, forming a shoulder 58 in the wall of the bore 48. The collet 46 rests on the shoulder 58 and is held in the bore by rounding over the body 44 at the end 56. The open end 56 is sized to guide the rounded end 58 of the pin 52 into the bore 48. The collet 46 is of resilient copper beryllium alloy material to British Standard BS 2870, Designation CB 101W (hardness 390 VPN minimum) and is split along its length (see Fig. 2) to allow it to be compressed when it is held in the enlarged region 54 of the bore 48. Two cantilevered legs 60 extend radially inwardly into the bore 48, in the direction of insertion of the pin end 58. As the pin end 58 is inserted into the bore 48 through the collet 46 the legs 60 are urged outwards and so grip the pin 52, forming an electrical contact between the pin 8 and the socket 10. The collet 46 extends along about 30% of the length of the bore 48. Each leg 60 occupies about half the length of the collet and subtends an angle of about 45 degrees at the bore axis and projects into the bore 48 at an angle of about 30 degrees to the bore axis. The pin 8 and socket body 10 are formed of brass to BS2874, Designation CZ131, VPN 110/140 and have ends 62, 34 for crimping or soldering to the wire leads 16, 34 as is known in the art. The pin 8, socket 10 and collet 46 are gold coated, with a relatively thick coating being applied only on the collet 46. The collet is plated with a 0.75 to 0.875 μm thick layer of gold on a 1.25 to 2.0 μm thick layer of nickel. A silver plating of about 2.5-3.0 μm on 3.7-5.0 μm nickel may also be used. The pin portion 52 and the end region 54 of the socket are plated with a 0.2 μm thick gold layer on a 3 μm thick nickel layer. The end 56 is rounded after the collet 46 has been inserted in the enlarged region 54 of the bore 48. The rounded end 56 serves to retain the collet 46 in the bore 48 and also guides the pin end 58 as it is inserted in the bore 48, preventing damage to the collet 46 if the pin 52 is initialy mis-aligned with the bore 48.

Claims: CLAI MS: 1. A pin and socket electrical connector comprising a first connector member having a plurality of socket contacts mounted in an electrically insulating dielectric, and a second contact member having a plurality of pin contacts mounted in an electrically insulating dielectric, the pin contacts being arranged to align with respective socket contacts, and means for coupling the connector members together to make the respective pin and socket contacts, wherein a socket has a body having a bore which is open at one end for receiving a respective pin, and a collet is housed in the bore in contact with the bore wall and arranged to contact the pin when it is received in the bore to form an electrical contact between the pin and the socket. 2. A connector as claimed in claim 1, wherein the collet is located adjacent the open end of the bore, the pin being inserted, in use, through the open end into the bore. 3. A connector as claimed in claim 1 or 2, wherein the open end of the bore is rounded over to retain the collet in the bore. 4. A connector as claimed in claim 1, 2 or 3, wherein the collet bears on a shoulder on the wall of the bore. 5. A connector as claimed in any one of claims 1 to 4, wherein the collet is split along its length and is compressed when housed in the bore. 6. A connector as claimed in any one of claims 1 to 5, wherein the collet has a leg which extends radially into the bore to grip the inserted pin, the leg being urged radially outward by the pin as it is inserted. 7. A socket for a pin and socket electrical connector, the socket comprising a body having a bore and a collet inserted in the bore, as defined in any one of the preceding claims.

Inventors: REES ALUN DAVID, REES, ALUN, DAVID
Applicants: AB CONNECTORS LTD, REES ALUN DAVID, AB CONNECTORS LIMITED, REES, ALUN, DAVID
Application year: 1994
Main classification: H01R13
IPC codes: H01R13